The noise of an running industrial fan or blower depends on the type of a fan, the machining accuracy and assembled conditions of each element, and buffs. Many studies have been carried out to reduce the noise through silencer in blower. In this study, 3 types of buffs which have different hole are employed in pipe of blower to study the influence the number and arrangement of buffs on the noise reduction at inlet and outlet in pipe. Commercial engineering software ANSYS was employed to analyze the characteristics and reduction ratio of pressure. Experimental results shows that optimal one can reduce the reduction ratio of noise as much as 16 percents in the laboratory. Good agreement was found between the analysed ratio of noise reduction and those obtained from the experiments.
Both microstructure and mechanical properties of C f /SiC composites were examined in this study. C f /SiC composites were fabricated by a liquid sintering process(LPS), using a commercial SiC powder with an average size of about 0.3 ㎛. C f /SiC composites were sintered at the temperature of 1820 ℃ under the applied pressure of 20 ㎫ for the pressure holding time of 1 hour. The sintering additives for the fabrication of LPS-C f /SiC composites were selected as a compound of Al₂O₃ and Y₂O₃ particles. The composition ratio(Al₂O ₃/Y₂O₃) of additive material and its total amount were 1.5 and 10 wt.%, respectively. Plain woven carbon fabrics were treated by a sizing process, prior to the preparation of fiber preform for the fabrication of LPS-C f /SiC composites. The fiber preforms were prepared by the infiltration of complex mixture slurry with SiC, Al₂O₃, Y₂O₃ powders and polyvinylbutyral(PVB) resin into the fabric structure.
??In this paper, the stability of a cracked cantilever Timoshenko beam with a tip mass subjected to follower force is investigated. In addition, an analysis of the flutter instability(flutter critical follower force) and a critical natural frequency of a cracked cantilever Euler / Timoshenko beam with a tip mass subjected to a follower force is presented. The vibration analysis on such cracked beam is conducted to identify the critical follower force for flutter instability based on the variation of the first two resonant frequencies of the beam. Therefore, the effect of the crack's intensity, location and a tip mass on the flutter follower force is studied. The crack section is represented by a local flexibility matrix connecting two undamaged beam segments. The crack is assumed to be in the first mode of fracture and to be always opened during the vibrations.
In this study, In order to prevent the safety accidents caused by the sliding, to develop the non-slip grating, the stability judgment based on the span length of the grating and the gap of the bearing bar is performed. The structural analysis of Grating was carried out in accordance with the provisions set out in Grating’s load-bearing test conditions.
As the span length increases, the deflection increases and the stress and span length tend to be proportional to each other. It was shown that the larger the span, the linear increase in stress and exponential increase in deformation of grating. The maximum stress of grating was approximately 58.2 MPa, indicating a very stable safety rate of about 4.3 compared to the yield strength of the grating material.
Based on these results, it will be able to be utilized as the basic data for determining the optimal dimensions of non-slip grading by performing optimal designs in the future.
The dynamic stability of elastically restrained cantilever pipe conveying fluid with crack is investigated in this paper. The pipe, which is fixed at one end, is assumed to rest on an intermediate spring support. Based on the Euler-Bernoulli beam theory, the equation of motion is derived by the energy expressions using extended Hamilton's Principle. The crack section is represented by a local flexibility matrix connecting two undamaged pipe segments. The influence of a crack severity and position, mass ratio and the velocity of fluid flow on the stability of a cantilever pipe by the numerical method are studied. Also, the critical flow velocity for the flutter and divergence due to variation in the support location and the stiffness of the spring support is presented. The stability maps of the pipe system are obtained as a function of mass ratios and effect of crack.
An iterative modal analysis approach is developed to determine the effect of transverse open cracks on the dynamic behavior of simply supported Euler-Bernoulli beams with the moving masses. The influences of the velocities of moving masses, the distance between the moving masses and a crack have been studied on the dynamic behavior of a simply supported beam system by numerical method. The Presence of crack results In large deflection of beam. The crack section is represented by a local flexibility matrix connecting two undamaged beam segments i.e. the crack is modelled as a rotational spring. This flexibility matrix defines the relationship between the displacements and forces across the crack section and is derived by applying fundamental fracture mechanics theory. Totally, as the velocity of the moving masses and the distance between the moving masses are increased, the mid-span deflection of simply supported beam with the crack is decreased.
The stability of a rotating cantilever pipe conveying fluid with a crack and tip mass is investigated by the numerical method. That is, the effects of the rotating angular velocity, mass ratio, crack severity and tip mass on the critical flow velocity for flutter instability of system are studied. The equations of motion of rotating pipe are derived by using the Euler-Bernoulli beam theory and the extended Hamilton's principle. The crack section of pipe is represented by a local flexibility matrix connecting two undamaged pipe segments. Also, the crack is assumed to be in the first mode of fracture and always opened during the vibrations. When the tip mass and crack are constant, the critical flow velocity for flutter is proportional to the rotating angular velocity of pipe. In addition, the stability maps of the rotating pipe system as a rotating angular velocity and mass ratio ${\beta}$ are presented.
In this paper the vibration system is consisted of a rotating cantilever pipe conveying fluid and tip mass. The equation of motion is derived by using the Lagrange's equation. Also, the equation of motion is derived applying a modeling method that employs hybrid deformation variables. The influences of a rotating angular velocity, mass ratio and the velocity of fluid flow on the stability of a cantilever pipe by the numerical method. The effect of tip mass on the stability of a rotating cantilever pipe is also studied. The influences of a tip mass, the mass ratio, the velocity of fluid, the angular velocity of a cantilever pipe and the coupling of these factors on the stability of a cantilever pipe are analytically clarified.
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